Structural properties of charge disproportionation and magnetic order in Sr2/3Ln1/3FeO3 (Ln=La, Pr, and Nd)

Abstract

The structural properties and the magnetic ground state of Sr 2/3 Ln 1/3 FeO 3 (Ln = La, Pr, Nd) samples were studied by means of synchrotron x-ray powder diffraction, neutron powder diffraction, and Mössbauer spectroscopy. All samples exhibit a metal-insulator-like transition coupled to a magnetic arrangement at a critical temperature, T MI . The diffraction techniques reveal strong structural changes at T MI that lead to new cells with reduced symmetry at low temperature. The new symmetry of the low-temperature phase has been determined for all compounds. The space groups are P3c1 for La-based compound and A2/n for the rest of samples. The high-resolution x-ray patterns detected superstructure peaks that can be accounted for by a small charge disproportionation between two nonequivalent Fe sites in the low-temperature phase explained in terms of a charge density wave that propagates along one of the body diagonals of the primitive cubic cell of these compounds. Our results clearly reveal that a full charge disproportionation of Fe 4+ into Fe 3+ and Fe 5+ is not produced. We have determined the magnetic ordering of these samples exhibiting an antiferromagnetic structure with a sixfold periodicity with respect to the primitive cubic structure. The magnetic group accounting for the magnetic arrangements was obtained by a symmetry analysis and it is C2/c (15.85) for all samples but with different unit cell depending on the type of FeO 6 tilts. The collinear ordering of Fe moments is established perpendicular to the charge density wave (along the body diagonal of the primitive cubic cell) and also perpendicular to the unique monoclinic axis.

Spin ordering and physical properties of NaPrFeWO6 and NaSmFeWO6 with polar double perovskite structure

“…This indicates that the magnetic arrangement follows the propagation vector k=(1/2, 0, 1/2) (A-point of the Brillouin Zone) as reported for related compounds [18]. We have used Isodistort program [33,34] to explore the magnetic irreducible representations for the nuclear cell with P21 symmetry. The search was limited to the A-point in agreement with the previous propagation vector.…”

Rare-Earth Regulation in the Crystal Structure, Electronic Structure, and Metal-To-Insulator Transitions of the High Oxygen Pressure-Annealed Re0.33Sr0.67FeO3

“…After the high-oxygen-pressure annealing, clear MIT behaviors were observed for La 0.33 Sr 0.67 FeO 3‑δ -O, Pr 0.33 Sr 0.67 FeO 3‑δ -O, and Nd 0.33 Sr 0.67 FeO 3‑δ -O. T MIT was obtained from the TCR- T shown in Figure S3a: 198, 189, and 183 K for Re 0.33 Sr 0.67 FeO 3 ( Re = La, Pr, and Nd), respectively. Since Re 0.33 Sr 0.67 FeO 3 ( Re = La, Pr, and Nd) grown in oxygen atmosphere show MIT behavior according to refs , the considerably high amount of oxygen vacancy is expected to be associated with the absence of the MIT behavior.…”

“…The crystal structure of Re 1−x Sr x FeO 3-δ was known to be related to the rare-earth elements Re, the ratio between Re and Sr, and also the oxygen vacancies, and such complexity accounts for the variations in their structures reported previously. In previous research, the space group of Re 0.33 Sr 0.67 FeO 3 was expected to be R3̅ c [11][12][13]15,16,20,31 for Re = La, and the space group can be summarized as Imma for Re = Pr, Nd, and Gd. 15,17,32 Although for Re = Sm both space groups Pm-3m and Imma were reported, herein the space group of Sm 0.33 Sr 0.67 FeO 3 is more likely to be Pm-3m, which is consistent with ref 33.…”

Structural and magnetic properties of Ca3Mn2−xRuxO7(0<

“…In order to solve the magnetic arrangement, a symmetry analysis was performed using the program ISODISTORT [36] to explore the magnetic irreducible representations (mIrreps) for the nuclear cell with Bb2 1 m symmetry. This strategy was used previously to solve magnetic structures in related perovskites [37]. The search was initially limited to and Y -points and the results are summarized in Table IV.…”